It is a very tight fit in the tunnel.
But, I think all of that is on me.
I replaced entire suspension in the car with UMI and the "Stage 2" is a 2 inch drop.
In addition, I have a Strange S-60, so I think the rear geometry is altered and to get the best angle I could, I put in adjustable lower control arms and rotated the rear axle to get the pinion "up" and ended up with 3* tranny, 1* driveshaft and 3* pinion, so I have a 2* front and rear delta to keep the line in in parallel.
I did have a transmission mount that I cut the sides off and re-welded to make a 1/2 inch mount, and that got the unit clear of touching the tunnel, but then my engine was getting too much pitch up, and I would have had to cut the rear lower ends off a bit to get more adjustment, but then my angles would be pushing to a point that I would need a box of U-Joints and transmission rear seals in the trunk to drive as much as I do.
So, it has a bit of a "rumble" from the drivetrain transmitted to the body, but I rode Harleys so what's a little vibration among friends? :D
I will fix this after I get my '68 built and on the road, but in spite of that little bit, I am very happy indeed, both the "fun" of banging all them gears and being able to "grab a quick lower" at the press of a button, and the drivability at highway speeds without feeling like I need to grab another gear, is great.
(I had my car on jack stands, so I was unable to swing a hammer as well as I would like to get the clearance by stretching the tunnel in the tight spots)
But, I think any stock suspension should not be a problem other than making a couple of "dents" about the size of a quarter where the top mount bosses on the unit might touch the tunnel. (and even running your hand over the carpet after, they are very hard to find).
And mine has a button on the shifter. GV sends a black ball with the GV logo, but EPCO Manufacturing is the folks who make the balls for GV, and I had already used them for my original ball, so I called and sent them a sample of color to match and they sent me a ball with my shift pattern and the button in the same spot.
This is the "physics package".
This is how it was shipped...
(Don't make me push the button...)